Carbon resistor rheostat



A. SHARENQW CARBON RESISTOR RHEOSTAT Dec.. 12, 1950 2 Sheets-Sheet 1 Filed Oct. l5 1948 t/ [fle 34d 3(20.

A SHARENOW CARBON RESISTOR RHEOSTAT FIGA Dec. 12, 1950 Flled oct 15 1948 Patented Dec. 12, 1950 lUNII'EI) STATES PATENT OFFICE Application (October t15, 1948, Serial No. 54,658

The ksubi ect of this invention relates to carbon disc i;heos'tats, such as are intended particularly for'regu).ating the voltage in ymotor circuits and especially those of fractional horsepower bythe compression of said discs.

My invention vhas =tor its object to provide a carbon disc controller of an improved construe.-

which it is possible -to obtain a gradual 3 Claims. Cl. 2101-48) controllable resistance operating over a wider range `of current variation without overheating.

lmother object of my invention is to provide certain improvements in vthe construction of carbon disc current controllers whereby the various parts may be readily assembled and those which are subjected to resistance heating are readily ventilated to prevent them from overheating due to the resistance interposed ina power circuit in which the rheostat is placed.

A still further object of my invention is to provide a special casing and the mounting therein of a resistance of the type aforementioned in conjunction with an operating treadle by means .oi which the voltage in an electric circuit may be regulated to a nicety.

To these and other ends my invention Coinprises `further improvements and advantages .as will be iurther described in the accompanying specification, the novel features thereof being set :forth in the appended claims.

in the drawings:

Figure i is a side elevation of a resistor Limit embodying my invention showing the saine mounted in its casing, the latter being shown as it appears in section longitudinally.

Figure -2 is a horizontal sectional View taken on the line 2-2 of Fig, l.

Figure 3 is a Side elevation ot the two part porcelain casing containing the circuit control elements.

Figure e is a top plan View of the casing as seen in Fig. 3.

Figure 5 is an interior View of one oi" the two similar sections of the casing as seen when viewed along the line -ii of Fig. 3, and

Figure 6 is an enlarged end view similar to Fig. i as seen when looking in the direction indicated by the section line 6 5 of Fig. 2.

Similar reference numerals, in the several iigures, indicate similar parts.

In carrying out my invention I provide a controller having two parallel piles of carbon resistance discs lo and l! as shown in Fig. 2. Each pile is composed of a large number of discs which being very thin are difficult to handle Without injury. In addition to this I have learned in practice that in transmitting current there is often a tendency for certain of the discs, or the pile as a whole, to become overheated. Therefore, in order to aid in the assembly of the piles and prevent overheating of the discs I provide a special form of mounting for them.

The mounting proper comprises duplicate parts arranged face to face in .spaced relation and which may be d enel as a lower or bottom member i2 and an upper or top member I3, each being of insulating material, preferably moulded porcelain. The mounting as a whole is generally rectangular in out'iine. .et its rear end is a transversely extending recess it and at its forward end is a throughway opening i5 having spaced parallel walls i6. At the bottom oi said opening there is a passage il connecting it with the recess It. The two ends of this passage are or different diameters thus providing it midway with a shoulder i8.

Referring new to Fig. 5 which is an interior view of one of the members of the mounting, said members being duplicates, the above `described iea'tures will be seen in addition to \.vh ich there are shown the parallel semi-circular grooves or depressions ita-I la for the reception of the disc piles lEi-i i. At the vforward end of these grooves are apertures 28-21 which terminate in the outer flat end faces 22-23 of the mountings from which there extend outwardly short projections 2li- 25 one edge of each of which forms an extension -for one 0f the side walls of the recess l5. The extensions Ztl-2&3

0n the respective members i2 and i3 do not meet on their proximate edges, but are separated, as indicated at 26 in Fig. 3, and at their bottoms each is recessed in line with the end faces i-23, as shown at 2l 2la.

The purpose of the described construction of the forward ends of the members `i2--i3 is as follows: In the ends of the grooves ille-Aia I provide Contact elements against which one end of the disc piles are compressed. They are of metal and comprise flat circular heads 3o having on their outer sides short necks Si lying in the recesses 2-2l. Extending inwardly on each of the faces 22-23, bridging the parting line between the members |2-i3 of the mounting, and projecting through the recesses `2 TJ-Zla are flat plates 3I-3i"-, the proximate free ends of which form circuit contact members. Terminals for an electric circuit comprise other plates 32--321 having fastening portions extending at right angles t0 the plates si-sl lying in close engagement with the outer edges of the projections 24-25 and having outwardly bent ends carrying binding parts such as screws The respective pairs of contact plates and terminals are each secured to the necks 3l by screws 3ft-6e which are threaded into said necks.

The opposite ends of the pile grooves are also apertured, as indicated at dil-li in Fig. 5, for the reception of the bodies 42 or carbon buttons (Fig. 2) which serve as the pile compressors. Each of these buttons, it will be observed in Fig. 2, is provided with a iiange 43 which limits it outward movement.

Compression of the discs composing the piles IIJ- H and a circuit established through them is'accomplished by means of a cross piece lying in the recess I4. It comprises an inner contact strip 53 of copper and an outer stiffener or backing plate I, these two plates being united rigidly at the center by a tubular bushing 52. The latter is of such diameter as to add to the stiffness of the backing plate 5l and prevent its distortion in the area of the perforation in which the bushing is mounted. rIhis contact-compression element is loosely mounted on an operating rod 53 the extremity of which projects through said bushing and is circumferentially upset in a series of points 565 to bear against it.

The forward end of rod 53 extends through the central opening in the mounting, as shown in Fig. 2, to a point well beyond the contacts 3i-3i9v and is threaded. At an intermediate point on this threaded end there is a rectangulare plate 55 guided at its ends by the faces i6 of the recess l5 of the mounting and having a .Ef

central threaded hub 55 for facilitating its adjustment or initial setting by rotating the rod in which position it is secured by a lock nut 51.

Plate 55 has two upturned ears 58-59a which at the time the rod is moved forwardly to compress the disc piles will engage the contacts Iii-Sla which latter although they have a slight spring action are limited in their movement by the recesses 2li-21a so that no strain is imparted to their fastenings {i4-35e. Rod 53 is normally held in its retracted, open circuit position by a coil spring 69 which is compressed between the cross piece 5t and the shoulder i8 in the control opening in the mounting.

YOn the free end of rod 55 there is a threaded knob or head 5l of insulating material the adjustment of which regulates the throw imparted by the movement of the operating treadle.

In assemblingthe above described parts the lower member l2 of the mounting is placed in a horizontal position on the work bench and the disc piles with their end contact members and compressing buttons are placed, as shown in 2, in the respective recesses 19a, 20 and 10. It is also convenient at this stage to assemble on Ythe rod 53 the various parts carried thereby and lay these in the mounting member.

|lhere are four'bolt holes in the members l2 and i3 (Figs. 2 and 5) two for bolts for initially securing said members together, the others vfor use in mounting the assembly within a casing. Perforated `gasket pieces 52 are laid in registration with the rst mentioned bolt holes and the other member i3 is superposed thereon andsecured by two through bolts E3. this assembly hold the faces of the members I2 and E3 separated torprovideV a Ventilating opening, such as indicated by Se in Figs. 1 and 3, through which air may circulate for the purpose of cooling the disc piles.

The rheostat herein set forth is finally mounted in a casing as shown in Fig.Y 1 which is a rectangular framework comprising a base 65 having rubber foot pieces 56 at the corners and carrying a cover S1 to which the rheostat is rigidly attached as by bolts 68 passing through the parts |2-|3.

As a convenience in attaching the cover to the base I provide at one end of the base an offset lip 69 beneath which lan inwardly extending flange on the cover can be hooked. At the opposite end of the base there is struck up a projection 'H for receiving the threaded end of a screw 12 on the cover. n j

A A, treadle 13 is pivoted between ears 14 on the The gaskets in top of the cover and is yieldingly held in a normally inoperative position by a coil spring 15. The treadle carries on the underside an arm 16, the lower bifurcated end of which straddles the hub of the knob 6I of the rheostat. It will be seen that upon depressing the treadle the rod 53 will be drawn forwardly against the tension of its spring 60 to establish a circuit across the terminals 3l-3Ia and that the cross arm 5I will simultaneously compress the disc piles to a greater or less degree depending upon the arc through which the treadle is depressed. Y

I claim:

l. A casing for a carbon disc rheostat comprising a pair of two rectangular members of insulating material of given thickness, length and width, placed face to face, each of said members having two lengthwise grooves in their proximate faces extending parallel to each other and spaced apart to furnish control areas in the members, said groove being in mating relation and adapted torhouse piles of carbon discs therein, fastening means extending through said central areas for securing the pair of members together, and spacers for holding the proximate faces of the members apart.

2. In a carbon disc rheostat, a casing comprising two similar members of insulating material having fiat faces adapted to be juxtaposed, each member having on ,its face two semi-circular longitudinally extending parallel semi-circular grooves spaced apart and in mating relation, said member also having longitudinal mating cavities located between the grooves for receiving piles of Vcarbon discs, the ends of said grooves being of reduced cross section and opening at opposite ends of the members, one end of the members adapted to have stationary contact members in the reduced portions thereof, the other ends of the members yadapted to have movable contacts in the reduced portions, and means for securing Vthe members together.

3. In a carbon disc rheostat mounting of insulating material, a casing comprising a two part rectangular body having at its forward end a at face `and a centrally located inwardly extending cut out with parallel side walls and provided with a longitudinal cavity leading from the bottom of the cut out, outwardly projecting lingers on the face in line with said faces of the cut out which are undercut to form openings in line with said end face, said body parts being further provided with mating semi-cylindrical grooves ladapted to receive piles of carbon discs arranged therein, and means for securing said part together in spaced mating relation.

ALEXANDER SHARENOW.

REFERENCES CITED The following references are of record in the of this patent:

UNITED STATES PATENTS Sweden Feb. 9, 1943 

